Pull cord for coverings for architectural openings and method of making same

ABSTRACT

A method of manufacturing a control cord for use in a covering for architectural openings includes the steps of providing spools of high tensile strength and low abrasion characteristic yarns, tensioning the yarns and winding the yarns under tension on bobbins, placing the bobbins in a braiding apparatus and making an eight-carrier braid from the yarns on the bobbins, and passing the braided cord through a treatment apparatus where a urethane coating is applied to the yarns and heat cured.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. application Ser. No.09/655,991, filed Sep. 6, 2000, pending. Application '991 is herebyincorporated by reference as though fully disclosed herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to pull cords used incoverings for architectural openings and more particularly to a braidedpull cord and the method of making the cord.

[0004] 2. Description of the Relevant Art

[0005] Most coverings for architectural openings, such as windows,doors, archways and the like, have an operating mechanism that iscontrolled by a flexible element that can be a fiber based cord, abeaded chain or the like. The control cord or the like typically dependsfrom one end of a headrail for the covering and extends into theheadrail through a friction brake and subsequently through carrierelements and around a plurality of pulleys and the like that areassociated with the operation of the covering. As a result, the controlcord is frictionally engaged at a number of locations and, dependingupon the frequency of operation of the covering and the abrasiveness ofthe elements with which the cord comes into contact, the controlelements can easily deteriorate.

[0006] In the case of fiber based cords, the abrasion caused by thevarious elements in which it comes into contact, causes rapiddeterioration of the cords. Cords that have deteriorated have to bereplaced and many operating cords in coverings for architecturalopenings are replaced on an annual basis. When the covering has beenwarranted, the replacement cost is borne by the manufacturer and,accordingly, the quality and longevity of control cords is a significanteconomic factor in the covering industry.

[0007] A typical fiber based cord used in coverings for architecturalopenings is braided from polyester fibers, with the cords typicallyincluding sixteen carrier fibers. After braiding of the cord, it is heattreated and wound on storage rolls before being incorporated into acovering product. The braid is relatively tight.

[0008] In trying to resolve the problem of rapidly deterioratingoperating cords, applicants initially looked to the hardware of thesystem to remove any abrasive surfaces across which the cord had topass. By redesigning various plastic molded parts and the parting linesin the plastic molds for the parts, the wear cycle was improved. Theredesigned components were later coated with low friction materials suchas Teflon® or zinc to reduce abrasion, but only marginal improvement wasnoticed. Further, the coatings tended to wear off over time and withexposure to UV light. Applicants then decided that the focus forimproving the wear cycle of operating cords needed to be on the corditself and it is to this end that the present invention has been made.

SUMMARY OF THE INVENTION

[0009] The cord of the present invention is made from high tensilestrength fibers with low abrasion characteristics, such as polyethylenefibers. The fibers are braided in an eight-carrier braid that is woundunder very high tension and ultimately finished with a urethane coatingthat is heat cured. The resultant product has provided a wear cycle ofmany times that achieved with state-of-the-art cords thereby almostremoving the problem of manufacturers in having to re-cord coverings forarchitectural openings. In accordance with the method for making theeight-carrier braid, high tensile strength fibers with low abrasion,such as might be polyethylene fibers, are wound under high tension ontoyarn bobbins and eight of the yarn bobbins are then utilized in aconventional braiding apparatus to braid the cord. The braided cord isheld under tension and passed through a two-stage heat setting processwherein a urethane coating is applied to the braided cord and thecoating is heat cured in the final stage. After the second stage ofheating, the cord is wound onto spools for storage until they are strunginto coverings for architectural openings.

[0010] Other aspects, features and details of the present invention canbe more completely understood by reference to the following detaileddescription of a preferred embodiment, taken in conjunction with thedrawings and from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a block diagram illustrating the steps in the process ofmaking the cord in accordance with the present invention.

[0012]FIG. 2 is a fragmentary diagrammatic isometric view showing yarnfrom which the cord will be braided being passed from supply spoolsunder tension to bobbins.

[0013]FIG. 3 is a fragmentary isometric illustrating the bobbinscarrying the yarns under tension and being positioned in a braidingapparatus and with the braided cord being wrapped on a storage spool.

[0014]FIG. 4 is a diagrammatic view showing yarn from storage spoolsbeing passed through a two-stage process for coating the yarns withurethane and heat curing the urethane on the yarn before accumulatingthe yarns on storage spools.

[0015]FIG. 5 is a fragmentary elevation showing the braided cord inaccordance with the present invention.

[0016]FIG. 6 is a diagrammatic elevation showing a prior art braidedcord.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017] The method of making a braided control cord for use in coveringsfor architectural openings in accordance with the present invention isillustrated in a block diagram in FIG. 1. It will there be appreciatedthat fibers or yarns from which the cord is to be braided are firstunwound from spools on which they are supplied and then wound under hightension onto bobbins. From the bobbins, eight yarns are braided into acord also under high tension and the braided cord is subsequently woundon a transfer spool. The cords are unwound from the transfer spoolsunder tension and fed into a treating apparatus where they are coatedwith urethane and immediately heat cured in a two-stage process so thatthe urethane coating is dried and fully cured on the braided cords.After the coating has been heat cured, the yarn is stored on storagespools from which it can be removed when incorporating the cord into anoperating mechanism for a covering for architectural openings.

[0018] With reference to FIG. 2, a device 10 for unwinding yarn 12 frompreformed spools 14 of yarn is shown in series with a conventionaltensioning apparatus 16 for the yarns and a conventional apparatus 18for wrapping the yarns on bobbins 20 under tension. To provide evengreater tension in the yarn than is provided by the conventionaltensioning apparatus 16, the yarns are passed through an additional butconventional washer tensioner (not shown) before they are received bythe tensioning apparatus 16. The device 10 for unwinding the yarn fromthe spools 14 can be seen to include a plurality of spindles 22 on whichthe spools 12 of yarn are disposed and the yarn is threaded through lowfriction ceramic guides 24 associated with each spool so that they canbe passed individually to the conventional tensioner (which is notshown) before passing on to the tensioning apparatus 16. In thetensioning apparatus, they are tensioned in a conventional manner withwasher tensioners 25 so that the yarns 12 when passed down to thebobbins 20 are fed to and wound on the bobbins under tension. Each ofthe devices and apparatuses 10, 16 and 18 are conventional items such asmanufactured by Ratera of Spain.

[0019] The yarns 12 have a high tensile strength in the range of 28-35grams/denier, and preferably 30 grams/denier, and have low coefficientsof friction, low abrasion characteristics and are durable from a flexfatigue standpoint. Examples of yarns that would be suitable for thispurpose are Kevlar manufactured by DuPont in the United States, Nomexmanufactured by DuPont, Twaron manufactured by Akzo of The Netherlands,Dyneema manufactured by DSM of Holland or Spectra manufactured by theAllied Signal Division of Honeywell, Inc., Petersburg, Va. The yarn orfibers are preferably polyethylene. The tension under which the yarns 12are wound on the bobbins 20 is preferably in the range of 115 to 140grams and desirably 120 grams.

[0020] Looking next at FIG. 3, the bobbins 20 with the yarn 12 woundthereon under tension, are placed in a braiding apparatus 26 of aconventional type such as of the type manufactured by Ratera of Spain.In the preferred embodiment of the invention, eight yarns are braidedinto a cord 27 and after braiding, wound onto a transfer spool 28. Thedenier of the yarns is preferably in the range of 275 to 375, which isgreater than the denier of yarns typically braided into control cords,as can be evidenced by reference to FIGS. 5 and 6, with FIG. 5 being acord braided in accordance with the present invention and FIG. 6 a priorart braided cord.

[0021] The transfer rolls of braided cord are then operatively connectedto a treatment apparatus 30 (FIG. 4) for final treatment of the cord.Each transfer spool 28 of cord is rotatably mounted on a bracket 32 onthe upstream end of the apparatus 30 so that the cord can be fed intoand through the treatment apparatus under tension via a conventionaltensioner 34. The tension in the cord is preferably in the range of150-200 g, with 150 grams being ideal. In the apparatus, 30 the braidedcord 27 is first fed through a chamber 36 where the cord is padded witha urethane coating that is applied to the cord. The chamber 36 is fedfrom a urethane reservoir 37. By way of example, the coating might beeither sprayed onto the cord or the cord might be drawn through a bathof the urethane in order to apply the desired coating to the cord. Thelatter is preferred. Immediately after the cord is coated with theurethane, it is passed through a heating chamber or oven 38 where theurethane is dried. The temperature in the heating chamber 38 ispreferably in the range of 120-140° C. even though temperatures outsidethat range would work as it would primarily affect the drying time.Subsequent thereto, the cord is passed through another heating chamber39 where the urethane is cured. The temperature in the curing chamber 39is preferably in the range of 100-120° C. even though, again,temperatures outside that range would work as the temperature primarilyaffects the curing time. The total time for drying and curing shouldideally be in the range of 60-120 seconds, with 90 seconds beingdesired. After the cord 27 has been padded with the urethane coating andcured, the final braided cord is wrapped onto a storage spool 40 that isrotatably mounted on brackets 42 at the downstream end of the apparatus34. When a predetermined supply of the braided cord 27 is wound onto thestorage spool 40, the spool is removed and retained for later use in theassembly of a covering for an architectural opening. The apparatus 30for treating the cord with a urethane solution and curing the cord isconventional and may be of the type manufactured by Andersson Mek ofSweden. The urethane solution is a mixture of urethane and water in aconcentration of 10% urethane by volume. The urethane is misciblein/with water and preferably itself comes from the chemical family ofpolyester, polyether polyurethane dispersions and can come from varioussources but a urethane marketed under the designation Baypret DLVDispersion Corporation by Bayer Corporation of Pittsburgh, Pa, has beenfound suitable for the cord of the present invention.

[0022] A cord formed in accordance with the present invention and asillustrated in FIG. 5, has been found to provide a wear cycle that isapproximately ten times that of conventional cords that are presently inuse.

[0023] Although the present invention has been described with a certaindegree of particularity, it is understood that the present disclosurehas been made by way of example, and changes in detail or structure maybe made without departing from the spirit of the invention as defined inthe appended claims.

1. A covering for an architectural opening comprising in combination:covering means for selectively covering and uncovering the architecturalopening by extension and retraction of said covering means; and anoperating mechanism mounted adjacent to said architectural opening andbeing operatively associated with said covering means, said mechanismincluding a control cord and operative elements frictionally engagedwith said control cord, said control cord being made from yarn having atensile strength in the range of 28-35 grams/denier and a denier in therange of 275-375.
 2. The covering of claim 1 wherein said yarn is madeof polyethylene.
 3. The covering of claim 1 or 2 wherein said cord ismade from said yarn that is braided.
 4. The covering of claim 3 whereinsaid yarn is wound on bobbins under a tension of 115-140 grams prior tobeing braided into said cord.
 5. The covering of claim 3 or 4 whereinsaid braided cord is placed under tension of 150-200 grams and coatedwith urethane prior to being incorporated into said operating mechanism.6. The covering of claim 5 wherein said braided cord is coated with amixture of urethane and water, then dried and cured prior to beingincorporated into said operating mechanism.
 7. The covering of claim 6wherein said urethane is a polyester, polyether urethane.
 8. Thecovering of claim 5, wherein said urethane is a polyester, polyetherurethane.